1. Field of the Invention
This invention relates to devices used for promoting blood circulation in body extremities and in particular to such devices which provide automatic means for enhancing blood circulation as well as a means to provide active participation of the patient.
2. Description of the Prior Art
Circulation devices shown in the prior art include U.S. Pat. No. 2,168,611, issued Aug. 8, 1939 to Thompson, which discloses a method of subjecting a plurality of parts of the human body to the changes of absolute pressure. The method comprises continuously moving gas into and out of two or more separate chambers such that a super atmospheric pressure is maintained in one chamber while a vacuum is maintained in one or more of the other chambers. U.S. Pat. No. 2,781,041, issued Feb. 12, 1957 to Weinberg, shows an apparatus for the progressive compression of body extremities. The apparatus comprises a sleeve for enclosing a human extremity made up of pressure applying cells positioned in end-to-end relation and an inner inflatable cell within and embracing the longitudinal extent of the first named cells and means for succcessive inflating the first cells and then the longer inner cell. U.S. Pat. No. 3,094,983, issued June 25, 1963, to MacLeod, shows a circulation assist device comprising a chamber for accepting a body extremity, the chamber having a seal for connection to the body extremity at one end and means for filling the chamber with liquid and means for varying the pressure of the liquid in the chamber. U.S. Pat. No. 3,783,859, issued Jan. 8, 1974, to Sauer et al, shows a circulatory assist device which utilizes the movement of a shell portion of a limb enclosing housing as a mechanical means for applying a requisite cyclic pressure to the limbs of a patient being treated. U.S. Pat. No. 3,865,103, issued Feb. 11, 1975, to Folman, shows a blood circulating device having a pair of airtight sleeves for encasing a body extremity, a slow air release valve in each of the sleeves and a source of compressed air connected to each sleeve at a point spaced from the valve for pulsatingly supplying air to each sleeve. U.S. Pat. No. 3,866,604, issued Feb. 18, 1975, to Curless et al, discloses a cardiac assist device which comprises a plurality of gas fillable bladders which are wrapped about a human limb and means for selectively inflating and deflating the bladders by the admission of gas into and withdrawal of gas from the bladders. U.S. Pat. No. 3,878, 839, issued Apr. 22, 1975, to Norton et al, shows a cardiac assist apparatus comprising a rigid housing having a pair of hingedly connected portions pivotally mounted relative to each other, means for clamping the portions together and a closed pneumatic pressure actuation means within the housing which provides pressure to the body extremity in synchronism with the patient's heart beat.